354 COMPARISON OF OVARIAN CONTENTS OF AKT ISOFORMS AMONG 4 STRAINS OF MICE

Abstract

Strain/individual differences in superovulation efficiency with gonadotropins constitute a serious problem in mouse reproduction (Suzuki et al. 1996 Reprod. Fertil. Dev. 8, 975–980). Because the PI3K/Akt signalling pathway is involved in ovarian folliculogenesis, quantitative difference of protein components in the PI3K/Akt signalling pathway among mouse strains may explain the strain difference in superovulation efficiency. The present study compared ovarian contents of AKT isoforms among 4 strains to examine the involvement of the PI3K/Akt signalling pathway in superovulation. Ovarian protein contents of AKT1, AKT2, and AKT3 isoforms in 4-week-old females of 4 mouse strains were measured by quantitative Western blots with GAPDH as an internal control using whole ovary homogenates (see Suzuki et al. 2011 Exp. Anim. 60, 193–196, for method details). Observed values were compared among strains by 1-way ANOVA after normality (Shapiro-Wilk) and equal variance (Levene) were confirmed. Ovarian protein contents of all 3 AKT isoforms in A/J, C57BL/6N, DBA/2, and C3H/He (arbitrary unit, mean ± s.e.m., n = 4) were significantly different among strains by 1-way ANOVA (P < 0.05). Ovarian AKT1 contents were 1.01 ± 0.10^a, 0.98 ± 0.07, 0.89 ± 0.03, and 0.84 ± 0.02^b, respectively. Ovarian AKT2 contents were 1.39 ± 0.13^a, 0.74 ± 0.10^b, 1.03 ± 0.07^c, and 0.91 ± 0.19^bc, respectively. Ovarian AKT3 contents were 1.24 ± 0.38, 1.55 ± 0.24^a, 1.11 ± 0.09, and 0.67 ± 0.18^b, respectively. ^a–cValues with different superscripts in each isoform are significantly different by Tukey test (P < 0.05). Thus, significant quantitative differences in ovarian AKT isoforms among strains suggest that the ovarian PI3K/Akt signalling pathway acts differently among strains. This activity difference of the pathway may explain the strain difference in superovulation efficiency in mice.

This work was supported by a grant from the Ministry of Health, Labour and Welfare of Japan.